betrayer vs nark

betrayer and nark both are nouns.

Word	Noun	Adjective	Verb	Adverb
betrayer	Yes	No	No	No
nark	Yes	No	Yes	No

As nouns, nark is a hyponym of betrayer; that is, nark is a word with a more specific, narrower meaning than betrayer:

betrayer: one who reveals confidential information to the police or other authority
nark: an informer or spy working for the police

betrayer (noun)	nark (noun)
a person who says one thing and does another	an informer or spy working for the police
one who reveals confidential information to the police or other authority	a lawman concerned with narcotics violations

betrayer (verb)	nark (verb)
	inform or spy (for the police)
	cause annoyance in; disturb, especially by minor irritations